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Biomedical subjects

S S Robertson

Publications and source records attributed to S S Robertson.

31 records · Page 2Linked to original sources
PubMed1986

The development of cyclic motility in fetuses of diabetic mothers.

The cyclic organization of spontaneous movement was studied longitudinally in 22 fetuses of diabetic mothers (FDMs) during the third trimester of gestation and quantified with spectral analysis. Cyclic motility at frequencies between .08 and 1.22 cycles/min was found in all fetuses, although it was temporarily absent in 12 of the 22 fetuses at some time between 25 and 38 weeks. While some parameters of cyclic motility changed little, the frequency of the dominant motility cycle doubled from .24 to .48 cycle/min between 28 and 36 weeks, and the relative strength of motility cycles in the band between .18 and 1.02 cycles/min decreased temporarily at 36 weeks. These developmental changes and the common absence of cyclic motility contrast sharply with previous findings in normal fetuses, and (except for its absence) are accounted for by a subgroup of FDMs whose mothers' blood glucose levels were least well controlled during the third trimester of gestation. The presence of cyclic motility in all FDMs provides further evidence that cyclic activation is a basic property of the developing central nervous system in the human, as it appears to be in other vertebrates. However, the differences between FDMs and normal fetuses suggest that the development of cyclic motility is sensitive to disturbances in the fetal metabolic environment.

Birth Weight↗
PubMed1986

Interaction between nonnutritive sucking and respiration in preterm infants.

The effect of nonnutritive sucking bursts (NNSBs) on respiratory frequency was sequentially evaluated in 12 healthy preterm infants. Studies were performed during active sleep in infants between 32 and 37 weeks postconceptional age. The duration of NNSBs was classified as follows: (a) less than 3 s, (b) between 3 and 6 s, and (c) greater than 6 s. NNSBs of each duration were found at all ages, although NNSBs greater than 6 s were the least frequently observed. Respiratory rate increased significantly during NNSBs of less than 3 s, and also in those of 3-6 s duration. There was no significant effect on respiratory frequency of sucking bursts longer than 6 s. Our results document an early interaction between these two motor rhythms, which is influenced by the length of the NNSB. Moreover, they indicate that the decrease in respiratory frequency reported in a similar group of preterm infants during feeding should not be interpreted as an effect of sucking per se.

Aging↗
PubMed1985

Cyclic motor activity in the human fetus after midgestation.

The spontaneous movements of human fetuses were studied longitudinally between 21 and 41 weeks of gestation. At each age, spectral analysis of the fluctuations in fetal movement revealed strong cyclic patterns. The frequency of the dominant motor rhythms ranged from .13 to 1.91 cycles per minute. The strength of oscillations between .18 and 1.02 cycles per minute increased slightly with gestation, but the frequency of the dominant motility cycle, the width of the corresponding spectral peak, and the incidence of weaker (usually faster) rhythms did not change. Neuromuscular activity is known to serve important developmental functions in the embryo and fetus. The ubiquity and relative consistency of cyclic motility in the last half of human gestation, and the existence of similar periodicity in other species, suggest that the cyclic activation of developing motor circuits may possess particular adaptive value.

Female↗
PubMed1985

Development of sucking rhythm in preterm infants.

We studied the ontogeny and temporal organization of non-nutritive sucking during active sleep in 6 healthy preterm infants (mean birthweight 1.1 kg (range 0.8-1.3 kg) gestational age 28.6 weeks (range 26-30 w] from 30 to 35 weeks of post-menstrual (PM) age. Recognizable rhythmical sucking bursts were recorded at 28 weeks in one infant and by 31-33 weeks in the others. Results were analyzed for the periods 30-31, 32-33 and 34-35 PM weeks. The number of bursts/min increased with age, while the duration of each burst was stable (mean 4.1 s). The pause between bursts decreased. Sucking pace within bursts increased with age which resulted in an increase in the overall rate of sucking. The coefficient of variation (CV) for intersuck time within bursts and for interburst time was computed to examine the stability of the sucking rhythm. For intersuck time the CV was relatively low and constant across ages. However, for interburst time CV was relatively large across ages. Thus, there appears to be a stability of the intraburst sucking rhythm from 30 weeks of gestation, whereas the interburst rhythm is less regular. This documentation of temporal organization in sucking from 30 weeks is one of the earliest indications of an intrinsic rhythm in human behavior.

Aging↗
PubMed1985

Biphasic response of respiratory frequency to hypercapnea in preterm infants.

The time course of the transient ventilatory response to a sudden change in inspired gas from room air to 4% CO2 in air was examined in 11 healthy preterm neonates. Changes in minute ventilation (VI), tidal volume (VT), and respiratory frequency (f) were determined over 4 to 5 min of CO2 inhalation during both quiet (QS) and active sleep (AS) in each infant. In both states there was a brisk increase of mean VI in response to 4% CO2, while mean VT increased more slowly and mean f only increased transiently at 1 to 2 min. Exponential curve fitting to the change in VI and VT for each infant accounted for 64 +/- 20% of the variance in VI during QS as compared to 30 +/- 18% during AS (p less than 0.003). In only six infants did exponential curves fitted to the changes in VI and VT during QS reach 90% of their steady state values within 4 to 5 min of CO2 exposure. Their time to reach 90% of steady state was always shorter for VI than VT (p less than 0.01). Frequency showed a biphasic response with a transient rise at 1 to 2 min (p less than 0.05) and return to control levels at steady state. These data indicate that not all preterm infants reach a new level of steady state ventilation within 4 to 5 min of 4% CO2 inhalation. Furthermore, many infants exhibit a biphasic response of f over time which causes VI to reach steady state prior to VT.

Carbon Dioxide↗
PubMed1984

Transcutaneous oxygen tension during nonnutritive sucking in preterm infants.

The effects of nonnutritive sucking on transcutaneous oxygen tension, heart rate, and respiratory rate were studied sequentially in 14 sleeping preterm infants breathing room air. Transcutaneous oxygen tension increased during nonnutritive sucking in infants between 32 and 35 weeks postconceptional age, but not in those between 36 and 39 weeks. This response was not associated with a change in respiratory rate or sleep state, although heart rate tended to increase. These data offer further support for the beneficial effects of nonnutritive sucking in preterm infants.

Female↗
PubMed1982

Human fetal movement: spontaneous oscillations near one cycle per minute.

Spectral analysis of spontaneous fluctuations in human fetal movement revealed strong oscillations at frequencies between 0.24 and 0.90 cycle per minute, which are much higher than those of the cyclic alternation of quiet and active states in the fetus and neonate. Oscillations at frequencies up to 2.88 cycles per minute were also detected, but they were usually much weaker. The prominent peaks in the fetal movement spectra are in the frequency range of recently reported neonatal motor rhythms, and indicate the existence of a cyclic process controlling spontaneous motor output that oscillates near one cycle per minute and begins to function in utero.

Female↗
PubMed1982

Relationship between transcutaneous and arterial oxygen tension in sick neonates during mild hyperoxemia.

The effect of mild hyperoxemia on the relationship between transcutaneous (PtcO2) and arterial PO2 (PaO2) was determined in a group of 68 neonates with cardiopulmonary disease. In contrast to the relationship during normoxemia which did not differ from the line of identify, PtcO2 underestimated PaO2 by 17 +/- 9 torr (p less than 0.001) at PaO2 values ranging from 100-140 torr. Considerable caution, therefore, must be exercised in exclusively employing PtcO2 monitoring in neonates whose PaO2 is to be maintained near 100 torr.

Arm↗
PubMed1982

Intrinsic temporal patterning in the spontaneous movement of awake neonates.

The temporal organization of spontaneous movement in healthy, awake neonates was studied on the second or third day after birth. Movement was recorded using time lapse photography and quantified as a function of time. Fourier analysis was then used to partition the total variance of each neonate's time-based data into independent components in the frequency domain. Tests on the resulting cumulative variance distributions indicated that the fluctuations in movement over time were not random. Smoothed spectral density functions were then computed to isolate the dominant rhythms. Spectral peaks occurred in the region between .24 and 1.86 cycles per min, indicating the presence of rhythms in general motility with an average frequency (across babies) of .69 cycles per min. These findings are evidence of intrinsic temporal organization at frequencies very different from previously documented rhythms in newborn behavior and physiology.

Activity Cycles↗
PubMed1980

Event perception by children in the early stages of language production.

The distribution of attention to the actors in a visual event and the influence of linguistic variables on attention were studied. 1-word and 2-word children viewed a filmed event that portrayed a brief agent-action-recipient sequence in the presence of a nonparticipant. The event was accompanied by linguistic input that was general or named an actor. A habituation paradigm was used with a cardiac response measure. Response recovery to brief occlusions of the actors in the test trials indicated the existence of a neutral period before the action began during which attention was evenly distributed across the actors. During and after the action, the agent commanded a priority in the distribution of attention. Naming an actor had a strong directing influence on attention in the neutral period and more limited effects on attention during and after the action. There were no effects of sex or language status.

Attention↗